The present invention relates to materials useful for lowering the pour point of wax-containing mixtures of liquid hydrocarbons, as well as compositions of, and methods for preparing the same. More particularly, this invention relates to methods of using and the use in liquid hydrocarbons of compositions containing units derived from (i) hydrocarbyl(meth)acrylic acid derivatives and (ii) ethylenically unsaturated aliphatic α-olefin monomers having up to 50 carbon atoms. The compositions can be mixtures and/or copolymer compositions and are useful for modifying the fluidity and flow characteristics of liquid hydrocarbons, and more particularly, for improving the pipeline pumpability of liquid hydrocarbons.
Crude oil production provides one example of issues flowability of liquid hydrocarbon compositions. Offshore crude oil production often necessitates the flow of crude oil through undersea pipelines. Sub-sea temperatures can be and often are as low as approximately 4° C. Crude oils contain components, such as, for example, paraffins, alkanes, etc., that at these low temperatures tend to precipitate as large crystals. These crystals can agglomerate to form a gel structure which can precipitate in the pipe, causing a reduction in the flow rate of the crude oil through the pipe.
The problems with wax creation in crude oil, among other liquid hydrocarbons, have led to chemical and mechanical methods for removing the wax deposits. However, mechanical methods in particular often result in equipment down-time, meaning loss of production, and increased engineering costs. Accordingly, effective chemical methods, in which chemical additives are fed into the pipe lines are often more desirable. A number of additives are known in the art, and include wax crystal modifiers such as pour point depressants and wax dispersants. These chemical additives depress the temperature of formation of the wax crystals and can modify the wax morphology (for example, by reducing the size of the crystals that form) thereby reducing the propensity of the wax to adhere to the pipe-line walls or block filters.
A large portion of the prior art references in this area teach pour point depressants comprising maleic anhydride, among which references include, for example, U.S. Pat. Nos. 3,536,461; 3,574,575; 3,879,177 and 4,284,414. Some references teach the use of acrylate type polymers including, for example, U.S. Pat. Nos. 6,255,261; 6,750,305; 8,067,349; and 8,143,202.
There is a continual need to produce more effective polymers giving improved performance in liquid hydrocarbon compositions. For example, oil companies are encountering crude oils that are increasingly more difficult to handle. Generally these oils have higher pour points and increasing wax content (amount and chain length of paraffins, alkanes, etc.), meaning that new and more effective chemistries are required.